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Biochemistry > L11 revised > Flashcards

L11 revised Flashcards

1
Q

what is the largest single tissue in the human body?

A

muscle

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2
Q

what are the 3 types of muscles present in the human body?

A

skeletal: striated , under voluntary nervous control
cardiac: striated , involuntary

and smooth : non striated, involuntary

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3
Q

describe the structure of striated muscles

A

a single muscle is composed of thousands of muscle fibers that extend for variable distance along its longitudinal axis

each muscle fiber is a large and complex multinucleated cell

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4
Q

what are muscle fibers surrounded by ?

A

an electrically excitable plasma membrane called the sarcolemma

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5
Q

what do individual muscle fibers contain ?

A

many myofibrils arranged in parallel embedded in intracellular fluid called sarcoplasm

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6
Q

what are the parallel structures inside individual muscle fibers called ?

A

myofibrils

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7
Q

what is the intracellular fluid inside individual muscle fibers called ?

A

sarcoplasm

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8
Q

what is the functional unit of muscle called?

A

sarcomere

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9
Q

where do T tubules invaginate from ?

A

sarcolemma

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10
Q

how does myofibril appear under the microscope ?

A

shows alternating dark(A bands ) and light(I bands ) bands

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11
Q

what region of the A band appears slightly lighter than the rest of the band ?

A

the central region of the A band , Which is also called the H band

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12
Q

what is the I band bisected by ?

A

very dense and narrow z line

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13
Q

where can thin filaments be found ?

A

in the I band . they also extend to the A band but not into the H zone

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14
Q

what proteins do thin filaments contain ?

A

actin , tropomyosin , and troponin

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15
Q

how are thin filaments arranged ?

A

they are arranged around the thick (myosin ) filaments as a hexagonal array

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16
Q

where can thick filaments be seen ?

A

confined to the A band

17
Q

what protein do thick filaments contain ?

A

myosin

18
Q

how are thick filaments arranged ?

A

cross section as a hexagonal array

19
Q

what is monomeric actin called ?>

A

G actin \

it is globular

it makes up to 25% of muscle protein by weight

20
Q

when does F actin form?

A

when G-actin polymerizes in the presence of Mg2+ to form the insoluble helicat filament called f actin

21
Q

describe the structure of myosin

A

has a fibrous tail consisting of 2 intertwined helices

each helix has a globular head portion attached at one end

the hexamer consists of 2 heavy (H) chains and 4 light (L) chains

22
Q

what is tropomyosin ?

A

fibrous molecule that consists of 2 chains , alpha , and beta , that attaches to F actin in the grooves between its filaments

it is present in all muscles and all muscles like structures

23
Q

what is troponin ?

A

structure unique to skeletal muscles and consists of 3 poly peptides

24
Q

what are the three polypeptides of troponin , briefly describe each ?

A

Troponin T : bind to tropomyosin as well as the 2 other troponin components

Troponin I:inhibits the F actin- myosin interaction , also binds to other components of troponin

troponin C : is a calcium binding polypeptide .

4 molecules of calcium ion are bound per molecule of troponin C

25
Q

cardiac troponins help in diagnosing _____

A

myocardial infarction

26
Q

MUSCLE CONTRACTION AND RELAXATION ARE IN THE OTHER DECK AND PPT

A

..

27
Q

What is malignant hyperthermia ?

A

body temp rises on exposure to certain anesthetics and skeletal muscle relaxants

The reaction consists primarily of rigidity of skeletal muscles, hypermetabolism, and high fever.

28
Q

what is the function of dystrophin ?

A

it is a cytoskeletal protein that connects F-actin to the DG complex(dystroglycan )

dystrophin complex acts as an anchor connecting each muscle cells cytoskeleton with the frame work of extracellular matrix proteins .Also play a role in cell signalling by interacting with chemical signals.

29
Q

what happens if dystrophin is absent ?

A

In absence of dystrophin, plasma membrane of muscle cells gets damaged during contractile process leading to muscle cell death.

30
Q

what term is applied to diseases that cause progressive weakness of skeletal muscles ?

A

muscular dystrophy

Mutations in the genes for the various components of the dystrophin–glycoprotein complex are a prominent cause.

31
Q

Duchenne muscular dystrophy is ____?

A

is a serious form of dystrophy in which the dystrophin protein is absent from muscle

32
Q

Becker muscular dystrophy is ___?

A

Dystrophin is present but altered or reduced in amount.

33
Q

what is sarcopenia ?

A

Loss of skeletal muscle mass with age

Biochemistry (15 decks)

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